1. Field of the Invention
The invention pertains to the field of carbon-fiber laminates. More particularly, the invention pertains to musical instrument sound boards made of layers of carbon-fiber and resin with a core or base layer of specific material, and methods of making such sound boards.
2. Description of Related Art
The following US patents and published applications show stringed instruments with soundboards incorporating composite fiber materials:
U.S. Pat. No. 3,880,040 “Sound Board for Stringed Instrument” Kaman (1975) Guitar having a sound board made of layers of graphite fiber and a wood core. Core is plywood or veneer, may be single layer or multiple layers.
U.S. Pat. No. 4,334,452 “Plastic musical instrument body having structural insert” Morrison, et al [Norlin Industries, Inc.](1982)—a structural support member of wood is embedded within a plastic body, which is essentially solid (there is a cut-out hollow area). The thickness of plastic about the structural member at most points along the member is substantially minimized and the mass of plastic material on one side of the member is not substantially greater than the mass of plastic on the opposite side of the member.
U.S. Pat. No. 4,348,933 “Soundboard assembly for pianos or the like” Kaman, et al. [Currier Piano Company, Inc.](1982) A soundboard assembly for use in a piano, harpsichord or similar stringed musical instrument comprises a thin, laminated soundboard consisting of a center sheet of wood and two outer layers of composite material. The center wooden sheet has a substantially unidirectional grain and the two outer layers of composite material are made of unidirectional carbon fibers embedded in a resin matrix.
U.S. Pat. No. 4,353,862 “Method for making sound board” Kaman [Kaman Aerospace Corporation](1982)—A fiber glass fabric reinforced wood sound board for a guitar is made by placing a sheet of wood in a shallow mold cavity with a layer of fiber glass fabric overlying an associated surface of the wood sheet, spreading a layer of liquid resinous compound over the layer of fabric to impregnate the fabric, providing a plate having a smooth surface, positioning the plate with its smooth surface in face-to-face engagement with the layer of liquid impregnating material to provide a substantial closure for the mold cavity, drawing vacuum on the mold cavity, and curing the liquid resinous material.
U.S. Pat. No. 4,364,990 “Construction material for stringed musical instruments” Haines [University of South Carolina] (1982)—Uses cardboard or paper core covered in carbon-fiber material.
U.S. Pat. Nos. 4,873,907 and 4,969,381 “omposite-materials acoustic stringed musical instrument” Decker, Jr. et al. [Kuau Technology, Ltd.] (1989/1990)—soundboard for an acoustic guitar made of a composite-materials plate having an area density matching that of wooden soundboards while having a bulk density exceeding the bulk density of wooden soundboards. The soundboard is preferably made of a lay-up of woven polymer (preferably aramid) fabric and a layer of unidirectional graphite fibers followed by a layer of decorative fabric (e.g., silk), all embedded in a resin matrix.
U.S. Pat. Nos. 5,125,312 and 5,189,235 “Stringed Musical Instrument” Fishman, et al [Korg/Fishpark Associates] (1992/1993) A light weight guitar with light weight wood core material, strengthening layer of carbon fiber and a fiberglass sheet layer both impregnated with a high temperature resin. This is a solid-body guitar, the wood core is 1.5 inches thick.
U.S. Pat. No. 5,469,769 “Soundboard for musical instruments” Sawada et al. [Yamaha Corporation] (Nov. 28, 1995)—laminated construction soundboard for use pianos, the core having larger shearing elastic modulus and/or smaller shearing loss tangent than that of the fore and rear plates.
U.S. Pat. No. 5,952,592 “Acoustic guitar assembly” Teel (1999) An acoustic guitar having a resin laminate soundboard with a bracing pattern specifically configured to provide the non-wooden soundboard with qualities resembling traditional wooden soundboards.
U.S. Pat. No. 6,087,568 “Acoustically tailored composite material stringed instrument” Seal (Jul. 11, 2000)—guitar made up of a plurality of plies of composite laminates individually selected and arranged together to provide desired sounds.
U.S. Pat. No. 6,107,552 “Soundboards and stringed instruments” Coomar, et al.[Kuau Technology, Ltd.] (2000)—Soundboard includes first and second opposed layers of a stiffened graphite sheet material and a low-density foam core material interposed between the first and second opposed layers.
U.S. Pat. No. 6,294,718 “Stringed musical instrument top member” Saunders, et al. [Kaman Music Corporation] (2001)—Soundboard includes an outer composite material layer and an inner composite layer with a core layer, preferably wood, bonded between the inner and outer layers. Referring to FIG. 5, the composite material layers extend outboardly from the outer periphery of the interior portion and are bonded in contact with each other to form the core free flex edge portion of the forward part.
U.S. Pat. No. 6,372,970 Stringed musical instrument body and neck assembly Saunders, et al [Kaman Music Corporation] (2002)—Sound board has an outer composite material layer and an inner composite layer with a core layer, preferably wood, bonded between the inner and outer layers.
U.S. Pat. No. 6,664,452 “Acoustic guitar having a composite soundboard” Teel [C. F. Martin & Company, Inc.] (2003)—acoustic guitar having a hollow body constructed with a pre-finished graphite soundboard and a pre-finished high pressure laminate backboard and sidewall. A bracing pattern particularly for use with the graphite soundboard is also provided.
Published Application No. 2004/60,417 “Solid body acoustic guitar” Janes, et al. (Apr. 1, 2004)—A guitar body is formed of a generally solid material having a cavity formed therein and substantially lacking a soundboard. A soundboard is formed of a generally planar material attached to the solid material, so as to substantially cover the cavity. The planar material can be composite graphite.
Published Application No. 2002/104,423 “Composite stringed musical instrument, and method of making the same” Verd (Aug. 8, 2002)—acoustic and electrically amplified stringed musical instruments comprising fiber-reinforced resin composite materials, where the instruments are provided with a sound-damping interior coating.
Published Application No. 2002/69,743 “Soundboard of composite fibre material construction” Schleske (Jun. 13, 2002)—a soundboard for acoustic musical instruments constructed as a composite fiber sandwich plate consisting of core plate and fiber coating. The fiber coating is characterized in that it is multidirectional and single-layer, or multidirectional and applied only to part-zones of the core plate.
Published Application No. 2002/66,354 “Soundboard of composite fibre material construction” Schleske (Jun. 6, 2002)—a soundboard for acoustic musical instruments produced as a composite fiber sandwich. The core plate of the sandwich construction is provided with at least one recess.
Published Application No. 2002/66,353 “Soundboard of composite fibre material construction” Schleske (Jun. 6, 2002)—a soundboard for acoustic musical instruments constructed as a composite fiber sandwich plate. The area defined by the outline of the soundboard is enlarged relative to the average area of the soundboards of conventional musical instruments of the same type in such a way as to compensate for the characteristic frequency shifts ( and thus changes in timbre) which result from the more favorable ratio of stiffness to mass of the composite fiber sandwich plate relative to the conventional solid wood soundboard.